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faster congruent modulo for points, fixes #83

This commit is contained in:
Josh Baker 2016-11-14 10:27:18 -07:00
parent e7b9d2e273
commit 5ec3111e8b
1 changed files with 7 additions and 3 deletions
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10
index/norm.go
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@ -1,13 +1,16 @@
package index package index
import "math"
// normPoint takes the latitude and longitude of one point and return the x,y position on a world map. // normPoint takes the latitude and longitude of one point and return the x,y position on a world map.
// The map bounds are minimum -180,-90 and maximum 180,90. These values are x,y; not lat,lon. // The map bounds are minimum -180,-90 and maximum 180,90. These values are x,y; not lat,lon.
func normPoint(lat, lon float64) (x float64, y float64, normd bool) { func normPoint(lat, lon float64) (x, y float64, normd bool) {
// Check if the rect is completely in bounds. This is likely to be the vast majority of cases. // Check if the rect is completely in bounds.
// This is likely to be the vast majority of cases.
if lon >= -180 && lon <= 180 && lat >= -90 && lat <= 90 { if lon >= -180 && lon <= 180 && lat >= -90 && lat <= 90 {
return lon, lat, false return lon, lat, false
} }
// TODO: replace loops with math/mod. lat = math.Mod(lat, 360)
for lat < -90 || lat > 90 { for lat < -90 || lat > 90 {
if lat < -90 { if lat < -90 {
lat = -90 - (90 + lat) lat = -90 - (90 + lat)
@ -18,6 +21,7 @@ func normPoint(lat, lon float64) (x float64, y float64, normd bool) {
lon = 180 + lon lon = 180 + lon
} }
} }
lon = math.Mod(lon, 360)
for lon < -180 { for lon < -180 {
lon += 360 lon += 360
} }